A fishy tale of long and short life span
Fish have wide variations in life span even within closely related species. One such example are the rockfish species found along North Pacific coasts, which have life spans ranging from 11 to more than 200 years. Kolora
et al
. sequenced and performed a genomic analysis of 88 rockfish species, including long-read sequencing of the genomes of six species (see the Perspective by Lu
et al
.). From this analysis, the authors unmasked the genetic drivers of longevity evolution, including immunity and DNA repair–related pathways. Copy number expansion in the butyrophilin gene family was shown to be positively associated with life span, and population historical dynamics and life histories correlated differently between long- and short-lived species. These results support the idea that inflammation may modulate the aging process in these fish. —LMZ
Background
Lacerta viridis
and
Lacerta bilineata
are sister species of European green lizards (eastern and western clades, respectively) that, until recently, were grouped together as the
L. viridis
complex. Genetic incompatibilities were observed between lacertid populations through crossing experiments, which led to the delineation of two separate species within the
L. viridis
complex. The population history of these sister species and processes driving divergence are unknown. We constructed the first high-quality
de novo
genome assemblies for both
L. viridis
and
L. bilineata
through Illumina and PacBio sequencing, with annotation support provided from transcriptome sequencing of several tissues. To estimate gene flow between the two species and identify factors involved in reproductive isolation, we studied their evolutionary history, identified genomic rearrangements, detected signatures of selection on non-coding RNA, and on protein-coding genes.
Findings
Here we show that gene flow was primarily unidirectional from
L. bilineata
to
L. viridis
after their split at least 1.15 million years ago. We detected positive selection of the non-coding repertoire; mutations in transcription factors; accumulation of divergence through inversions; selection on genes involved in neural development, reproduction, and behavior, as well as in ultraviolet-response, possibly driven by sexual selection, whose contribution to reproductive isolation between these lacertid species needs to be further evaluated.
Conclusion
The combination of short and long sequence reads resulted in one of the most complete lizard genome assemblies. The characterization of a diverse array of genomic features provided valuable insights into the demographic history of divergence among European green lizards, as well as key species differences, some of which are candidates that could have played a role in speciation. In addition, our study generated valuable genomic resources that can be used to address conservation-related issues in lacertids.
We sequenced the mitochondrial genome of the Western green lizard (Lacerta bilineata) using Illumina technology and additional Sanger sequencing. The assembled 17 086 bp mitogenome had a GC content of 40.32% and consisted of 13 protein-coding genes, 22 tRNA genes, two rRNA genes, and one control region (CR), with a gene order identical to the chordate consensus. In addition, we re-sequenced the mitogenome of the closely related Eastern green lizard L. viridis using the same techniques as for L. bilineata. The mitogenomes of L. bilineata and L. viridis showed a sequence identity of 94.4% and 99.9%, respectively, relative to the previously published L. viridis mitogenome. The phylogenetic reconstruction based on 17 Lacertinae mitogenomes using Anolis carolinensis as the outgroup supported L. bilineata and its sister species L. viridis as distinct lineages.
A high quality benchmark for small variants encompassing 88 to 90% of the reference genome has been developed for seven Genome in a Bottle (GIAB) reference samples. However a reliable benchmark for large indels and structural variants (SVs) is yet to be defined. In this study, we manually curated 1235 SVs which can ultimately be used to evaluate SV callers or train machine learning models. We developed a crowdsourcing app -SVCurator -to help curators manually review large indels and SVs within the human genome, and report their genotype and size accuracy.
A high quality benchmark for small variants encompassing 88 to 90% of the reference genome has been developed for seven Genome in a Bottle (GIAB) reference samples. However a reliable benchmark for large indels and structural variants (SVs) is more challenging. In this study, we manually curated 1235 SVs, which can ultimately be used to evaluate SV callers or train machine learning models. We developed a crowdsourcing app-SVCurator-to help GIAB curators manually review large indels and SVs within the human genome,
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